Effervescent tablets for cleaning tooth prostheses are known, consisting substantially of carbonates and/or biocarbonates, solid organic acids as citric acid, tartaric acid and similar materials, phosphates and/or polyphosphates, monosulpho-peracids, wetting agents, binders, cleansing agents, antimicrobials, indicators and other materials.
Furthermore, multilayer effervescent tablets for the cleansing of tooth prostheses are known, in which one layer containing a calcium-binding organic acid initially dissolves, superficially pre-cleansing the prosthesis. The second layer is intended to effect a fine-cleaning or after-cleaning by removing the deposits which are already attacked by the action of the first layer.
All these systems, though, have one disadvantage which will be explained below. It should be kept in mind that the soiling of a prosthesis may be basically divided into three groups as follows:
1. Food scraps of a fatty or fatty-viscous character (desserts, sauces, fruit ices) PA0 2. Adhering proteins (meat, milk product deposits) PA0 3. Poorly soluble mineral deposits arising from saliva (like tartar).
Most cleansing agents for prostheses work very well on group 1, less well on group 2, but almost not at all on group 3. The reason is that wetting agents and oxygen-producing substances are capable of removing fatty substances and combatting development of odors due to decay. However, it is not that easy to remove proteins, which is only possible when the proteins are mixed into the fatty material and can be removed together with it. Most of these methods do not succeed when these proteins strongly adhere to the prosthesis and the prosthesis is badly soiled with such materials. All these methods are completely unsuccessful in connection with tartar-like mineral deposits, which form after long use of a prosthesis without cleansing of a lattice-like substance wherein proteins are deposited.
The known prosthesis cleansing materials principally fail in this instance because tartar deposits can only be dissolved in strongly acidic media and thereby removed. Cleansing of fats and their removal by dispersing agents is logical only at pH's above 7, because cleansing by dispersing agents and particularly splitting off of oxygen at pH's below below 7 are technically not possible.
Thus in principle, are three mechanisms of action needed when it is desired to combat all three causes of soiling when cleansing a prosthesis.
Due to the fact that it is not possible to prepare a cleansing agent which is simultaneously acidic and alkaline, an invention must provide a multi-component tablet within which an acidic and an alkaline component differ in solubility. The purpose of this composition is to keep the pH of the cleansing solution at a preferred, for instance acidic level, initially for a definite time and progressively move the pH into the opposite, alkaline region in order to exert the cleansing power against all three soiling factors.
Here, basically two procedures are possible: the multi-component tablet may begin in the acidic region and after a certain time change into the alkaline region. The other possibility is to regulate the process in the opposite direction, in other words, to begin with alkalinity and thereafter change into the acidic region.
The former procedure is advantageous insofar as the tartar-like mineral deposits are initially dissolved which, due to their micro-crystalline structure, adhere especially strongly to the rough, scratched or mechanically damaged surface of the prosthesis. The easily actuated dissolution of the fatty layer progressively occurs in the alkaline environment.
If sulpho-peracids, dispersing agents, polyphosphates, perborates and similar substances are used for the removal of fatty components, it is also advantageous when these components are the latter ones. It is also advantageous to add in the same time span where this alkalinity is active, cleansing enzymes too, which become active for protracted times after the change from acidic to alkaline reaction. Most cleansing enzymes develop their principal activity in a pH region between 7 and 9 but cleansing enzymes are also known which act in the acidic region.